The present invention relates to an electromagnetic actuator for the control of the valves of an internal combustion engine.
As is known, internal combustion engines are currently being tested in which the intake and exhaust valves which bring the combustion chamber of the engine selectively into communication respectively with the intake manifold and the exhaust manifold of the engine are actuated by electromagnetic actuators driven by an electronic control unit. This solution makes it possible to vary the lift, opening time and moment of opening and closing of the valves as a function of the angular velocity of the crankshaft and other operating parameters of the engine, thereby substantially improving its performance.
In FIG. 1, the electromagnetic actuator I which currently provides the best performance is disposed alongside the stem of the valve II of the internal combustion engine to be axially moved and comprises:
an oscillating arm III of ferromagnetic material having a first end hinged on a fixed support IV so as to be able to oscillate bout a horizontal axis of rotation A perpendicular to the longitudinal axis of the valve II, and a second end connected via a hinge V to the upper end of the valve II of the engine to be axially moved;
a pair of electromagnets VI disposed on opposite sides of the body of the oscillating arm III so as to be able to attract on command and alternatively the oscillating arm III, causing it to rotate about the axis of rotation A;
and lastly an elastic member adapted to maintain the oscillating arm III in a rest position in which it is equidistant from the polar heads of the two electromagnets VI so as to maintain the valve II of the engine in an intermediate position between the closed position and the position of maximum opening that the valve II assumes when the oscillating arm III is disposed in contact with the polar head of the upper electromagnet VI and respectively with the polar head of the lower electromagnet VI.
The main drawback of the electromagnetic actuator I described and illustrated above is that the hinge V, as it has to be dimensioned to withstand, without the risk of breakage, propulsive mechanical stresses of substantial size (the oscillating arm III has to raise or lower the valve II in extremely short times), has a substantial weight and dimensions, substantially limiting the overall performance of the device. The mass of the hinge V in fact represents a considerable proportion of the overall mass of the moving parts.
The need to withstand, without the risk of breakage, propulsive mechanical stresses of substantial size, also makes it necessary, for the construction of the oscillating arm III and in particular the hinge V, to use particularly costly production processes and materials which have a major impact on the actuator""s overall production costs.
The object of the present invention is to provide an electromagnetic actuator for the control of the valves of an internal combustion engine that is free from the above-mentioned drawbacks.
According to the present invention, there is provided an electromagnetic actuator for the control of the valves of an internal combustion engine which comprises at least one variable volume combustion chamber, at least one connection duct adapted to bring the combustion chamber into communication with atmosphere and at least one valve adapted to regulate the passage of fluids from and to the combustion chamber, wherein this valve is axially movable between a closed position in which it closes off the connection duct, and a position of maximum opening in which it enables the passage of fluids through the connection duct with the maximum admissible flow, and wherein the electromagnetic actuator comprises an oscillating arm having a first end hinged on a fixed support and a second end connected to the valve and a pair of electromagnets adapted to cause the oscillating arm to rotate on command in order axially to displace the valve between the closed position and the position of maximum opening, this electromagnetic actuator being characterised in that it comprises a first elastic member adapted to maintain the valve in the closed position, and in that the second end of the oscillating arm is disposed in abutment on the valve so as to be able to transmit only an axial thrust contrary to that of the first elastic member.